Decorative lamp



FIG. 1 is a perspective view of our design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a right side elevation view thereof. 

The ornamental design for a decorative lamp, as shown and described. 